The Hell Wyrm is massive, around one kilometre long. On the front of its head is a massive spike, made of bone, and its eyes are further back, behind the first ring.
It is stone-grey in colouration, except for the four magical rings. One is around the head, there is one in each wing and one on the tail. The two in the wings allow the Hell Wyrm to fly, and the two around the head and tail are capable of creating devastating magical spells.
The Hell Wyrm is listed in The True Faith of Emiria as one of the three beings that threatened to destroy Mythos, the other two being Kalessaros the Black and Arkatekkon. Like the others, it is known that the Hell Wyrm was imprisoned soon after its creation, though how, where and by whom remains unknown.